It is known to provide flat strap materials, such as belts, webs and the like, hereinafter referred to as straps, with buckles or other connectors at an end of the strap for connection to another connector member which interfits with the first-mentioned connector, for receiving the other end of the strap, or in a similar or even different manner to allow connection of the first-mentioned strap end to another member or strap end.
Separable connectors, for example, for this purpose can include male and female members, the male member having a pair of deflectable elements which can lock in windows of the female member while a central tongue extends from the male member into the female member as a guide.
A disadvantage with such systems, described in German Pat Nos. 511,410 and 1,199,937, U.S. Pat. No. 4,150,464, and Swiss Pat. No. 554,151 is that considerable force is necessary to operate the connector or, where less force is required or the device is relatively simple, as in the aforementioned U.S. patent, it is necessary to carefully align the parts before they are fitted together.
In such connectors and buckles generally, it is also known to pass the strap through a slot in the buckle or connector, the slot being defined in part by a movable bar which is so oriented with respect to the way in which the strap is passed through the loop or around this bar, that tension on the strap draws the bar more tightly against the strap and thereby increases the clamping force and resistance to slip of the strap as tension increases.
The connectors and buckles of the invention can be utilized for a variety of purposes, including luggage, tie-downs for slipless adjustment of the affected length of the strap, in rucksacks and shoulder bags, for shoulder straps for a variety of other purposes and even for belts and straps for life preservers and even for fastening articles or loads in places.
One of the problems with such self-tightening clamping systems is that it is possible for the movable bar to tilt into such a position that it jams in its guides and is incapable after such a jamming of effectively clamping the strap.
The problem appears to arise from the fact that to allow free passage of the strap before the traction is applied and clamping is to ensue, it is necessary to provide a bar with some play in its guide. When the guide consists of a pair of guide slots receiving the rectangular or square end bar with play, therefore, it is possible for the bar to twist somewhat so that corners of the rectangular ends can brace or jam against opposite flanks of the guide groove and prevent effective clamping movement. The problem can of course be eliminated by the use of a round bar, but in this case the clamping action is less effective.